Such dual interface cards (contact/contactless) are known in the prior art. In the field of fabricating such cards, it has been usual to laminate several layers of material forming a card with an antenna (for example a wire antenna) embedded in the card body for the contactless communication.
Once a card element has been prepared, it is necessary to create a recess in the card element, usually by milling, in order to form the space in which a chip module is to be inserted and to free the contact portions of the antenna which is embedded, said contact portions being connected to contact pads of the chip module once said module has been inserted in the recess.
In general all these operations are done in two milling steps. The first one uses a milling tool with a large diameter to go fast and form a “standard” contact cavity.
The second one uses a smaller milling tool to make two small holes in order to reach the antenna pads.
Accordingly, these two steps can be done on a given piece of equipment only if it includes two milling stations
Milling steps are however not practical and have many drawbacks. For example, they induce internal mechanical stress in the laminated layers which may end in defects, delamination, deformation of the card etc.
Technically, the milling is very difficult to carry out in order to avoid misalignment or damaging the contact portion of the antenna for example.
Hence, due to these milling steps, such cards are produced only one by one which is expensive and time consuming.
Once the milling operation has been done, the chip module is inserted in the recess. Generally thermo glue is added (in the recess or on the back of the module) in order to achieve the attachment of the module to the laminated layers. The module is then shortly subjected to high temperature and pressure, typically one second at 180° C., in order to be fixed definitively in the recess. The insertion of a chip module in a laminated card is a weak point in that the chip module is only held by gluing and may detach itself from the card, for example when the card is bent.
In this process, the electrical connection of the contact pads of the module to the antenna is generally achieved by depositing a conductive glue on the contact portions of the antenna and configured such as that once the module is fixed in the recess, the pads of the module are also embedded in the conductive glue. The problem is that the short temperature increase (one second at 180° C.) carried out to fix the module in the recess is not long enough to fully cure the conductive glue, and as such is not sufficient to create a stable and optimal electrical connection between the module and the antenna. Accordingly, the finished cards are traditionally submitted to an extensive additional curing step in an oven, for example at 50° C. for 48 hours, that is extremely time consuming.
There are some publications in the state of the art showing how to manufacture dual interface cards without the milling step. Each of the disclosed methods has its drawbacks.
Publication US 2006/0163367, the entire contents of which are hereby incorporated herein by reference, discloses a dual interface smart card having an improved structure. This publication recognizes the problems of conventional fabrication processes using the milling step indicated above and only indicates that the chip module (“COB”) is connected with the antenna, then that the antenna or the sheet layer provided with the antenna and at least one intermediate layer and/or a printed layer are piled up before the lamination process, the card body and COB being integrated as one body using a lamination process. In particular, in the process described, the COB is mounted and connected to the antenna first, then a communication test is carried out, and then only an adhesive can be applied. Preferably in this publication, the antenna contact portion has only one line to minimize the overlap portion between the antenna terminal and the COB.
Another publication mentioning the problems of alignment and connection between antenna and chip module is WO 00/25265, the entire contents of which are hereby incorporated herein by reference. However, in this document, an alternative way of creating the recess is disclosed. The first way consists in laminating the different layers together and then forming the recess in the laminated layer. Typically, this can be done by milling and this process corresponds exactly to the one described above as being the prior art.
The second way is firstly to punch holes in the layers and then to laminate the layers together hence forming the recess by alignment of the punched holes. Once the recess has been created either by milling or by lamination of punched layers, then the chip module can be inserted in the recess. It is fixed in the recess by an electrically conductive adhesive film, said film being also used to realize the contact between the chip module and the antenna.
A further prior art is document DE 199 41 637, the entire contents of which are hereby incorporated herein by reference. In this publication, the idea is to avoid the additional step of providing an electrically conductive glue before inserting the chip module in the recess. According to the idea disclosed, a printed antenna is made of a conductive paste that is still soft when the module is placed in the recess, in order to allow a better penetration of the contact pads of the module in the material of the antenna. Then one applies heat punctually in order to activate the conductive paste.
EP 0 671 705, the entire contents of which are hereby incorporated herein by reference, relates to a process for making a dual-interface card. In this process, to create the recess, one overmolds the layer supporting the antenna with another layer, except at the place where the antenna contacts are situated in order to allow the contact with the chip module. By using this process, there is then no need to use a specific milling step as described above.
U.S. Pat. No. 4,897,534, the entire contents of which are hereby incorporated herein by reference, shows another method for producing a data carrier having an integrated circuit (IC). In this device, there is no connection to an antenna. In addition, in the process the various layers forming the card including the substrate bearing the IC a pressed together using heat and pressure. Hence, this prior art is not concerned with the connection of a chip module in the recess of a card and the creation of said recess.
U.S. Pat. No. 6,677,186, the entire contents of which are hereby incorporated herein by reference, discloses a method for making an electronic device in particular a contactless card. Firstly a chip is placed in a recess which is larger than the size of the chip. A hot lamination is applied in order to melt material from the recess and embed the side of the chip. Then, a layer carrying a printed antenna is applied with the contact pads of the antenna contacting the contact pads of the chip. A second hot lamination is applied in order to fix the sheets together and to allow the pads of the chip to penetrate in the (soft) material of the printed antenna pads. In one variation, the step of insulating the sides of the chip and the step of connecting the chip to the antenna are performed during a single lamination. This method is not disclosed for dual interface or contact cards, and only for (printed) antenna made of soft material.
U.S. Pat. No. 6,957,481, the entire contents of which are hereby incorporated herein by reference, discloses a method for making contactless cards with a chip and is directed mainly to the connection of the chip to the antenna. In the process disclosed metallized protrusions are produced on two contact pads on the chip and the connection of the chip to the antenna is effected by embedding the metallized protrusions in the thickness of the antenna, at the time that the chip is attached to said antenna.
WO 2007/065404, the entire contents of which are hereby incorporated herein by reference, further discloses a dual interface chip card and process for making said chip card. In this prior art, in order to avoid a milling step, the described fabrication process needs two lamination steps, a first one after contacting the pads of the antenna with the pads of the chip module after which step the direct contact side of the chip protrudes from the laminated layers. Then a second lamination process is carried out in order to add the layers so that the chip is flush with the surface of the card.